Congenital Anomalies of the Spine

Question 1

What is disjunction?

Question 2

• Separation of the neural tube from cutaneous ectoderm (immediately after, the cutaneous ectoderm fuses in the midline, dorsal to the neural tube.
• At same time perineural mesenchyme surrounds the neural tube - becomes meninges, bony spinal column, paraspinous musculature (should be isolated from central canal)

Question 3

Abnormal premature disjunction results in what?

Answer 3

Typically - spinal lipomas/lipomyelomeningoceles.

• This occurs when perineural mesenchyme gains access to the neural groove before closure of the neural tube.
• This is what happens rostral to the conus medullaris - if at conus or distal - this results from abnormal development of the caudal cell mass.

Question 4

What can failure of disjunction cause?

Answer 4

Dermal sinus tract or dermal-sinus like stalk (solid stalk composed of fibrous tissue and fat)

• In these cases mesenchyme can’t migrate between the neural ectoderm and cutaneous ectoderm at the site, which forms a focal spina bifida.
• Open spinal dysraphism (OSD) - (Myelocele and Myelomeningocele) can be explained by a large area of nondisjunction.

Question 5

The caudal cell mass forms in close anatomic proximity to the cloaca, which is the region of origin of what?

Answer 5

the lower GU tract and anorectal structures

• So, if anorectal/urogenital anomalies - high incidence of lumbosacral hypogenesis, tethered cord, terminal myelocystocele.

Question 6

In patient’s with vertebral anomalies (ie VACTERL, Klippel-Feil, Lumbosacral hypogenesis), look for what?

Answer 6

Associated spinal cord abnormalities (the development of the vertebral column is under similar factors as the spinal cord) - and same as the thoraci/abnodminal viscera.